Microplastics and Nanoplastics in Aquatic Environments: Aggregation, Deposition, and Enhanced Contaminant Transport

Abstract

Plastic litter is widely acknowledged as a global environmental threat, and poor management and disposal lead to increasing levels in the environment. Of recent concern is the degradation of plastics from macro- to micro- and even to nanosized particles smaller than 100 nm in size. At the nanoscale, plastics are difficult to detect and can be transported in air, soil, and water compartments. While the impact of plastic debris on marine and fresh waters and organisms has been studied, the loads, transformations, transport, and fate of plastics in terrestrial and subsurface environments are largely overlooked. In this Critical Review, we first present estimated loads of plastics in different environmental compartments. We also provide a critical review of the current knowledge vis-à-vis nanoplastic (NP) and microplastic (MP) aggregation, deposition, and contaminant cotransport in the environment. Important factors that affect aggregation and deposition in natural subsurface environments are identified and critically analyzed. Factors affecting contaminant sorption onto plastic debris are discussed, and we show how polyethylene generally exhibits a greater sorption capacity than other plastic types. Finally, we highlight key knowledge gaps that need to be addressed to improve our ability to predict the risks associated with these ubiquitous contaminants in the environment by understanding their mobility, aggregation behavior and their potential to enhance the transport of other pollutants.

Irrigation Water Quality—A Contemporary Perspective

“…Nanotechnology is also used widely for water treatment for both groundwater and surface water sources [205,206], but its repercussions are still not well understood [207]. In 2018, the occurrence of nanoparticle size plastics (nanoplastics) were critically reviewed with respect to human health and growing global occurrence in freshwater [208,209]. Analytical methods capable of detecting and quantifying nanoparticles in complex aqueous matrices are lacking, increasing the challenge in tracking fate and transport of these particles [207].…”

Biofilm formation by marine bacteria is impacted by concentration and surface functionalization of polystyrene nanoparticles in a species‐specific manner

“…Degraded microplastics are associated with surface defects such as microcrack formation and bubbling or pitting, while the generated nanoplastics are frequently close to spherical in shape (Corcoran et al ., ; Cooper and Corcoran, ; Yousif and Haddad, ; Lambert and Wagner, ; Hüffer et al ., ; Hernandez et al ., ). The formation of nanoplastics in simulated marine environments has been shown to lead to the formation of fractal aggregates, and critical coagulation constants are often observed in the order of 10 −3 – 10 −2 M and 10 −2 – 10 −1 for multivalent and monovalent salts, respectively (Koelmans et al ., ; Gigault et al ., ; Alimi et al ., ). This suggests that nanoplastics may readily aggregate in marine environments, with this aggregation expected to depend on surface charge and the presence of coatings, such as exopolymeric substances produced by bacteria (Alimi et al ., ; Summers et al ., ).…”

A catchment‐scale perspective of plastic pollution

“…Problems in managing plastic pollution, however, begin even earlier in their life cycle. Indeed, recent reviews and theoretical models have indicated a large number of potential sources, fluxes and sinks of plastics across the wider environment (Alimi, Farner Budarz, Hernandez, & Tufenkji, ; Browne et al, ; de Souza Machado, Kloas, Zarfl, Hempel, & Rillig, ; Horton, Svendsen, Williams, Spurgeon, & Lahive, ; Wagner et al, ). While crude estimates of environmental plastic fluxes have been attempted, a more detailed understanding of the sources, fluxes and effects of these anthropogenic pollutants in time and space, and a more comprehensive quantification of their fate, is now required urgently to determine the risks to people and ecosystems across the globe (de Souza Machado, Kloas et al, ; Horton & Dixon, ; Nizzetto, Bussi, Futter, Butterfield, & Whitehead, ).…”